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So I have an '01 F-150 and the check engine light came on. I have a pocket OBD2 reader to check the codes and it said lean fuel bank 1&2. I had just hit 150k on the stock fuel pump so I went ahead and changed that and the fuel filter at the same time. Reset the check engine light and it came back on about an hr or so after driving it. I was thinking maybe the MAF or the O2 sensor, but wanted to get some ideas from other people.
My idea is that a rational diagnostic process should be followed before replacing parts! The cost of a fuel pump could have paid for that and more. One diagnostic suggestion is to have someone with a smoke machine check for intake vacuum leaks. There are TWO upstream O2 sensors and they are probably reporting a lean mixture truthfully. Mass air flow sensors sometimes respond to cleaning.
Replacing parts on a blind guesswork basis is rarely cost-effective.
It's no idling high, but it does have a rough idle. The fuel pump is motorcraft(190.00) later still same issue. Im getting ready to pull the throttle body and clean it as well as the pcv
I understand that it may not be cost effective but it truthfully needed a fuel pump anyhow, because there was almost no fuel pressure prior to the swap.
Fuel pump is new, fuel filter is new so there is only one other thing in the system that effects fuel pressure and that is the regulator.
A vacuum leak would not affect fuel pressure at the shrader valve on the rail because its before the fuel injectors. The fuel spray is adjusted by the ecm. It does not control how much pressure is in the lines it controls the injectors. The fuel pressure regulator controls the pressure before the injectors for a steady psi then then ecm takes it from there telling the injectors how.much fuel to spray into the cylinders based on input from various other sensors like oxygen, map, maf, tps, iac valve, air temp, coolant temp etc...
I have an '03 with that 4.2L v6. Been there, done that.
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